Wafer level camera module and method of manufacture

ABSTRACT

A method includes forming optical lenses on an ICD at the wafer level, rather than attaching a separate lens assembly. The lenses may be formed as an array of individual lenses or as multiple, e.g., two, arrays of individual lenses. The array of lenses may be coupled to an array of ICDs. The ICDs and individual lenses in the array assembly may be singulated to form individual digital camera modules. Additionally or alternatively, the ICDs and individual lenses may be singulated in separate steps.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/698,776 (now U.S. Pat. No. 8,456,560) filed Jan. 26, 2007 by at leastone common inventor, which is incorporated herein by reference in itsentirety.

BACKGROUND

1. Technical Field

This invention relates generally to digital cameras, and moreparticularly to digital camera modules mountable in host devices.

2. Description of the Background Art

Digital camera modules are currently being incorporated into a varietyof host devices. Such host devices include cellular telephones, personaldata assistants (PDAs), computers, etc. And, consumer demand for digitalcamera modules in host devices continues to grow.

Host device manufacturers prefer digital camera module to be small, sothat they can be incorporated into the host device without increasingthe overall size of the host device. Further, host device manufacturersdesire camera modules that minimally affect host device design. Further,camera module and host device manufacturers want the incorporation ofthe camera modules into the host devices not to compromise imagequality.

A conventional digital camera module generally includes a lens assembly,a housing, a printed circuit board (PCB), and an integrated imagecapture device (ICD). Typically, the components are formed separatelyand later assembled to create the digital camera module. That is, theICD is attached to the PCB, and then the housing is attached to the PCBso that the ICD is covered by the bottom of the housing. The lensassembly is mounted to the opposite end of the housing to focus incidentlight onto an image capture surface of the ICD. The ICD is electricallycoupled to the PCB, which includes a plurality of electrical contactsfor the ICD to communicate image data to the host device for processing,display and storage.

ICDs are vulnerable to damage and contamination, particularly before andduring the housing attachment process. For example, before the housingis attached to the PCB, the wire bonds are exposed to inadvertentcontact (e.g., during handling), which can cause damage. Further, theICD is vulnerable to contamination from particulate debris.Contamination of the sensor array (the image capture surface) may blockincident light, causing visible defects in images being captured by thedevice. Damaged ICDs may cause a decrease in product yield and anincrease in labor and material costs.

What is needed is a camera module design and method of manufacturingcamera modules that reduces the chance of damaging ICDs, results inhigher yield, results in a faster manufacturing throughput, is lessexpensive, and/or results in smaller device sizes.

SUMMARY

Embodiments of the present invention overcome problems associated withthe prior art, by providing a digital camera module with lenses formedat the wafer level. Embodiments of the present invention facilitatehigher yield, faster throughput, and lower manufacturing costs byeliminating the need to attach a lens assembly within a housing. In someembodiments, quality may improve due to less handling and fewermaterials. Also, because the module is fabricated at the wafer level,clean room technology may be employed to reduce the risk of ICD damageor contamination. Further, in some embodiments, the overall size of thedigital camera module may be reduced in all three dimensions.

In accordance with an embodiment, the present invention provides adigital camera module comprising an ICD including an imager; a firsttransparent element; a bonding agent coupling said ICD to said firsttransparent element without blocking incident light to said imager; anda second transparent element coupled to said first transparent element.In one embodiment, no portion of said first transparent element and saidsecond transparent element extends beyond the perimeter of the ICD. Thefirst transparent element may include a concave-convex section and saidsecond transparent element may include a convex-concave section. Thebonding agent may include a die-cut adhesive sheet and/or dispensedadhesive. The adhesive sheet and/or the dispensed adhesive may includeopaque material and/or waterproof material. The first transparentelement and the second transparent element may form an airgaptherebetween, and said first transparent element and said ICD may forman airgap therebetween. The second transparent element may be coupled tosaid first transparent element via a bonding agent. The secondtransparent element may be coupled to said first transparent element viamechanical interaction. The mechanical interaction may includecomplementary interlocking features formed on said first transparentelement and said second transparent element. Additional transparentelements can be added to further improve image quality.

In accordance with another embodiment, the present invention provides adigital camera module workpiece, comprising an ICD wafer including anarray of ICDs; a first transparent element array including an array offirst transparent elements, each first transparent element positionedover a respective one of said ICDs; and a second transparent elementarray including an array of second transparent elements, each secondtransparent element positioned over a respective one of said firsttransparent elements. In one embodiment, the perimeter of each firsttransparent element and its respective second transparent element doesnot extend beyond the perimeter of its respective ICD. The workpiece mayfurther comprise metallization coupled to the ICD. The first transparentelement array may be coupled to said ICD wafer via a bonding agent. TheICD wafer and first transparent element array may be backlapped. The ICDwafer may be plasma etched on the side opposite said first transparentelement array to form holes for accessing bonding pads. These holes arethen metallized to reposition electrical contacts on the bottom surfaceof the ICD, where solder balls can be attached to form a wafer levelpackage. The second transparent element array may be coupled to saidfirst transparent element array via a bonding agent. The secondtransparent element array may be coupled to said first transparentelement array via mechanical interactions. The mechanical interactionsmay include complementary interlocking features formed on said firsttransparent elements and said second transparent elements. Additionalinterlocking transparent elements may be added to further improve imagequality.

In accordance with yet another embodiment, the present inventionprovides a method for manufacturing digital camera modules comprisingproviding an ICD wafer including an array of ICDs; providing a firsttransparent element array including an array of first transparentelements; bonding said first transparent element array to said ICD wafersuch that each ICD corresponds to a respective first transparentelement; providing a second transparent element array including an arrayof second transparent elements; bonding said second transparent elementarray to said first transparent element array such that each firsttransparent element corresponds to a respective second transparentelement; singulating said ICD wafer into individualized ICDs;singulating said first transparent element array into individualizedfirst transparent elements; and singulating said second transparentelement array into individualized second transparent elements.

Singulating said ICD wafer may be performed prior to said bonding ofsaid second transparent element array to said first transparent elementarray. The method may further comprise backlapping said firsttransparent element array prior to bonding said second transparentelement array to said first transparent element array. The method mayfurther comprise plasma etching said ICD wafer. The plasma etchingproduces holes in said ICD wafer to access bonding pads. These holes arethen metallized to provide electrical contacts on the bottom surface ofthe ICD, where solder balls may be attached to form a wafer levelpackage. The plasma etching may also singulate said ICD wafer intoindividualized ICDs. The method may further comprise metalizing andpatterning said individualized ICDs. Both said singulating said firsttransparent element array and said singulating said second transparentelement array may occur after said bonding of said second transparentelement array to said first transparent element array. The method mayfurther comprise coupling at least one of said individualized ICDs to acircuit substrate via solder pad connectors.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described with reference to the followingdrawings, wherein like reference numbers denote like elements:

FIG. 1A is a perspective view of a digital camera module affixed to aprinted circuit board (PCB), in accordance with an embodiment of thepresent invention;

FIG. 1B is an exploded perspective view of the digital camera modulerelative to the PCB, in accordance with an embodiment of the presentinvention;

FIG. 2 is a cross-sectional view of the digital camera module affixed tothe PCB, in accordance with an embodiment of the present invention;

FIG. 3A is a top view of an ICD wafer, in accordance with an embodimentof the present invention;

FIG. 3B is a top view of a transparent element array, in accordance withan embodiment of the present invention; and

FIG. 4 is a block diagram illustrating a method of manufacturing adigital camera module at the wafer level, in accordance with anembodiment of the present invention.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providea thorough understanding of the present invention. Those skilled in theart will recognize that the present invention may depart from thesedetails. Further, details of well-known practices and components havebeen omitted, so as not to unnecessarily obscure the present invention.

Embodiments of the present invention overcome problems associated withthe prior art, by providing a digital camera module with lenses formedthereon at the wafer level. Embodiments of the present inventionfacilitate higher yield, faster throughput, and lower manufacturingcosts by eliminating the need to attach the lens assembly within ahousing. In some embodiments, quality may improve due to less handlingand fewer materials. Also, because the module is fabricated at the waferlevel, clean room technology may be employed to reduce the risk of ICDdamage and/or contamination. Further, in some embodiments, the overallsize of the digital camera module may be reduced, e.g., in all threedimensions.

FIG. 1A is a perspective view of a digital camera module 100 affixed toa printed circuit board (PCB) 110, in accordance with an embodiment ofthe present invention. Digital camera module 100 includes an ICD 102, afirst transparent element 104 affixed to ICD 102, a second transparentelement 106 affixed to first transparent element 104, and metallization206 of ICD 102. First transparent element 104 may be bonded to ICD 102via bonding agent layer 108, e.g., a die-cut adhesive sheet applieddirectly between the top surface of ICD 102 and the bottom surface offirst transparent element 104 and/or an evenly dispensed adhesive. Firsttransparent element 104 may be bonded to the second transparent element106, e.g., using adhesive, mechanical interaction, etc. Themetallization 206 of ICD 102 may be accomplished using conventionaletching, patterning and metallization processes, and may includedielectric material. As shown, the digital camera module 100 is alignedalong a focal line 114, centered with respect to ICD 102.

In one embodiment, second transparent element 106 includes a lens 112.Lens 112 may be a convex-concave lens, constructed of optical glass orother optical grade material. Although not shown, first transparentelement 104 may also have a lens constructed of optical glass or otheroptical grade material. (See lens 116 of FIG. 1B.) Also, as shown,metallization 206 may include a perimeter wall angled inwardly, so thatthe perimeter of the metallization 206 does not exceed the perimeterwall of the ICD 102.

FIG. 1B is a perspective view of digital camera module 100 explodedalong focal line 114 and relative to PCB 110, in accordance with anembodiment of the present invention. Digital camera module 100 includesICD 102, metallization 206, bonding agent layer 108, first transparentelement 104, and second transparent element 106.

As shown, ICD 102 includes an imager 120 capable of capturing imagesfrom incident light. In this embodiment, imager 120 includes a generallyrectangular perimeter, although other perimeter shapes are possible.Bonding agent layer 108 includes aperture 118, which may have the sameperimeter as the imager 120 to provide an unobstructed path for light topass therethrough, while still allowing a bond to be formed betweenfirst transparent element 104 and ICD 102. In another embodiment,aperture 118 may have a perimeter of a different size and/or shape thanimager 120. Bonding agent layer 108 may include an opaque adhesivematerial to block light from entering the imager 120 through areas offirst transparent element 104 and/or second transparent element 106other than through the lens elements 112 and 116. Additionally oralternatively, bonding agent layer 108 may include a waterproof adhesiveto prevent vapor and/or particulate matter from contaminating air gap204 or imager 120.

In this embodiment, first transparent element 104 includesconcave-convex lens 116 (bulging outwardly towards ICD 120 and away fromincoming light). Second transparent element 106 includes convex-concavelens 112 (bulging outwardly away from ICD 120 and towards incominglight). First transparent element 104 and second transparent element 106act to focus light onto imager 120. It will be appreciated thatadditional transparent elements may be used, e.g., to change focus.

PCB 110 includes bonding pads 122 for electrical connection with digitalcamera module 100, or more specifically with ICD 102. Although notshown, metallization 206 may have a patterned and metalized underside(see FIG. 2) corresponding to bonding pads 122. In one embodiment,digital camera module 100 and PCB 110 are soldered together. One skilledin the art will recognize that other types of electrical contacts (e.g.,male and female plug blocks) may be used.

FIG. 2 is a cross-sectional side view of the digital camera module 100along focal line 114 relative to PCB 110, in accordance with anembodiment of the present invention. As shown, digital camera module 100includes ICD 102, metallization 206, bonding agent layer 108, firsttransparent element 104, and second transparent element 106.

First transparent element 104 has a concave-convex lens element 116 anda seat portion 150, and second transparent element 106 has aconvex-concave lens element 112 and a seat portion 155. In oneembodiment, the perimeter of each of lens element 112 and lens element116 is round, and the diameter of each of lens element 112 and lenselement 116 is at least as long as the longest dimension of imager 120.As shown, seat portion 150 (shown in FIG. 2 as including upwardly anddownwardly projecting legs) enables first transparent element 104 torest level on ICD 102 and second transparent element 106 to rest levelon seat portion 150 of first transparent element 104. Although seatportion 150 and seat portion 155 are shown as including substantiallyplanar sections, one skilled in the art will recognize that they mayhave different shapes, including mechanical fit- or snap-togetherpieces.

When first transparent element 104 and second transparent element 106are assembled, lens element 112 and lens element 116 form an air gap 202therebetween. Further, since lens element 116 is disposed between theupper surface of first transparent element 104 and the lower surface ofseat portion 150, lens element 116 and imager 120 also form an air gap204 therebetween. It will be appreciated that other embodiments may nothave air gaps 202 and 204. In one embodiment, one of first transparentelement 104 or second transparent element 106 may have no lens focusingpower at all and/or may include only a substantially planar sheet.

Solder 200, e.g., solder pads, may be used to couple digital cameramodule 100 to PCB 110. Solder 200 effectively couples bonding pads 122of PCB 110 and the metallization 206, thus creating electricalconnection between ICD 102 and PCB 110.

FIG. 3A is a top view of an ICD wafer 300, in accordance with anembodiment of the present invention. As shown, ICD wafer 300 includes anarray of individual ICDs 102, each including an imager 120. Theindividual ICDs 102 may be formed together on a wafer, and laterseparated during the assembly process. The outline of each ICD 102 isdefined by horizontal dotted lines 302 and vertical dotted lines 304.

FIG. 3B is a top view of a transparent element array 306, in accordancewith an embodiment of the present invention. Transparent element array306 includes a plurality of individual transparent elements 308, eachincluding a lens element 310. The individual transparent elements 308may be formed together on a wafer, and later separated during theassembly process. In one embodiment, the individual transparent elements308 are sized and/or spaced apart such that each transparent element 308corresponds to a respective one of the individual ICDs 102 of ICD wafer300. One skilled in the art will recognize that individual transparentelements 308 of transparent element array 306 may include firsttransparent elements 104 and/or second transparent elements 106.Accordingly, lens elements 310 formed thereon may be lenses 112 and/orlenses 116. The outline of each transparent element 308 is defined byhorizontal dotted lines 312 and vertical dotted lines 314.

FIG. 4 is a block diagram illustrating a method 400 for manufacturing awafer level digital camera module, in accordance with an embodiment ofthe present invention. In step 402, an ICD wafer comprising an array ofICDs is provided. In step 404, a first transparent element arraycomprising an array of first transparent elements is provided. In step406, the first transparent element array is bonded to the ICD wafer,e.g., using a bonding agent layer between the first transparent elementarray and the ICD wafer. In step 408, the bonded assembly is backlapped,i.e., possibly a portion of the backside (the inactive side) of the ICDwafer and possibly a portion of the topside of the first transparentelement array, is removed. Backlapping planarizes one or both sides ofthe assembly, reduces the thickness of the assembly, removes anyundesired curvature in one or both sides of the assembly, andfacilitates planarity and parallelism of the top and bottom surfaces,etc. In step 410, the ICD wafer is plasma etched and singulated. Theplasma etching process creates holes through the ICDs to enableelectrical connection to the bonding pads on the front side of the ICDs.Plasma etching, dicing, or any other suitable means can be used forsingulating the IC wafer. The singularization process individualizes theICDs by, for example, plasma etching, laser cutting and/or mechanicalcutting). At this point, the singulated ICDs may be maintained in arrayform by the first transparent element array. In step 412, the backsideof the ICDs are patterned and metalized to create electrical connectionsto the ICD circuitry for connection to the PCB.

In step 414, a second transparent element array is coupled to thetopside of the first transparent element array, so that a respectivesecond transparent element of the second transparent element array isaligned with a respective first transparent element of the firsttransparent element array. The second transparent array may be coupledusing a bonding agent, complementary mechanical interactions (e.g. fit-or snap-together pieces), or any other suitable coupling mechanism. Instep 416, the first and second transparent elements of the first andsecond transparent element arrays are singulated, e.g., using mechanicalcutting, to create individual digital camera modules.

Many of the described features may be substituted, altered or omittedwithout departing from the scope of the invention. For example, otherlens configurations are possible, e.g., by adding or deleting lenses, bychanging lens shapes, by changing optical powers, etc. Further, the ICDand PCB may be combined into a single electronic component. The order ofassembly may also change. As yet another example, the steps of plasmaetcheing, metallization, and solder ball attachment can be omitted,using instead a wire bonding process to electrically couple bonding padson the top surface of the ICD (left uncovered by the transparentelements) to bonding pads on a PCB. These and other deviations from theparticular embodiments shown will be apparent to those skilled in theart, in view of this disclosure.

I claim:
 1. A digital camera module comprising: an image capture device(ICD), said ICD being completely embodied in an integrated circuit chiphaving a top surface and a bottom surface, said top surface of saidintegrated circuit chip including an imager, said imager being a sensorarray in said integrated circuit chip; a first transparent element; abonding agent coupling said first transparent element to said topsurface of said integrated circuit chip; a metallization layer on saidbottom surface of said integrated circuit chip; a second transparentelement coupled to said first transparent element; and one or moreadditional transparent elements configured for changing a focus distanceof said camera module; and wherein said metallization layer includes aperimeter that does not exceed a perimeter of said integrated circuitchip; said first transparent element includes a concave-convex sectionand said second transparent element includes a convex-concave section;said second transparent element is coupled to said first transparentelement via mechanical interaction; and said mechanical interactioncomprises complementary interlocking features formed on said firsttransparent element and said second transparent element.
 2. A digitalcamera module according to claim 1, wherein no portion of said firsttransparent element and said second transparent element extend beyondthe perimeter of the ICD.
 3. A digital camera module according to claim1, wherein said bonding agent includes an adhesive sheet.
 4. A digitalcamera module according to claim 3, wherein: said adhesive sheet definesan aperture over said imager; and said aperture is at least as large asthe larger of a perimeter of said imager and a lens portion of saidtransparent element.
 5. A digital camera module according to claim 3,wherein: said adhesive sheet is directly adhered to both said topsurface of said integrated circuit chip and a bottom surface of saidfirst transparent element; and said first transparent element is a lenselement.
 6. A digital camera module according to claim 3, wherein saidadhesive sheet includes opaque material.
 7. A digital camera moduleaccording to claim 3, wherein said adhesive sheet includes waterproofmaterial.
 8. A digital camera module according to claim 1, wherein saidmetallization layer includes a perimeter wall angled inwardly such thatthe perimeter of said metallization layer does not exceed the perimeterof said ICD.
 9. A digital camera module according to claim 1, whereinsaid first transparent element and said second transparent element forman air gap there between, and said first transparent element and saidICD form an air gap there between.
 10. A digital camera moduleworkpiece, comprising: an image capture device (ICD) wafer including anarray of ICDs, each of said ICDs being an integrated circuit chip formedin said wafer and including a top surface, a bottom surface, and animager, each said imager being a sensor array formed in a respective oneof said integrated circuit chips; a first transparent element arrayincluding an array of first transparent elements, each first transparentelement positioned over a respective one of said ICDs; a bonding agentcoupling each of said top surfaces of said ICDs to a respective one ofsaid first transparent elements; a metallization layer on a side of saidICD wafer opposite said first transparent element array; a secondtransparent element array including an array of second transparentelements coupled to said first transparent element array, each secondtransparent element positioned over a respective one of said firsttransparent elements; and one or more additional transparent elementarrays configured for changing focus distances of camera modules of saidcamera module workpiece; and wherein said metallization layer defines aplurality of perimeters, each of said perimeters associated with one ofsaid ICDs and not exceeding a perimeter of said associated one of saidICDs; each of said first transparent elements includes a concave-convexsection and each of said second transparent elements includes aconvex-concave section; said second transparent element array is coupledto said first transparent element array via mechanical interactions; andsaid mechanical interactions comprise complementary interlockingfeatures formed on said first transparent elements and said secondtransparent elements.
 11. A digital camera module workpiece according toclaim 10, wherein said ICD wafer and first transparent element array arebacklapped.
 12. A digital camera module workpiece according to claim 10,wherein said bonding agent includes an adhesive sheet.
 13. A digitalcamera module workpiece according to claim 12, wherein: said adhesivesheet is directly adhered to both a top surface of said ICD wafer and abottom surface of said first transparent element array; and said firsttransparent element array includes an array of lens elements.
 14. Adigital camera module workpiece according to claim 12, wherein: saidadhesive sheet defines a plurality of apertures, each of said aperturespositioned over said imager of a respective one of said ICDs; and eachof said plurality of apertures is at least as large as the larger of aperimeter of said imager of said respective one of said ICDs and aperimeter of a lens element of said respective one of said firsttransparent elements positioned over said respective one of said ICDs.15. A digital camera module workpiece according to claim 12, whereinsaid adhesive sheet includes waterproof material.
 16. A digital cameramodule workpiece according to claim 12, wherein said adhesive sheetincludes opaque material.
 17. A digital camera module workpieceaccording to claim 10, wherein: said ICD wafer is plasma etched on theside opposite said first transparent element array to form holes foraccessing bonding pads and to singulate said ICDs; and said singulatedICDs are maintained in array form by said first transparent elementarray.
 18. A digital camera module workpiece according to claim 17,wherein each of said plurality of perimeters of said metallization layeris angled inwardly such that each of said perimeters does not exceed theperimeter of said associated one of said ICDs.
 19. A digital cameramodule workpiece according to claim 10, wherein the perimeter of each ofsaid first transparent elements and its respective second transparentelement does not extend beyond the perimeter of its respective ICD. 20.A digital camera module according to claim 10, wherein: each of saidfirst transparent elements and said respective second transparentelement form an air gap there between; and each of said firsttransparent elements and said respective one of said ICDs form an airgap there between.